Spin-conservation propensity rule for three-body recombination of ultracold Rb atoms

Abstract

We explore the physical origin and the general validity of a propensity rule for the conservation of the hyperfine spin state in three-body recombination. This rule was recently discovered for the special case of 87 Rb with its nearly equal singlet and triplet scattering lengths. Here, we test the propensity rule for 85 Rb for which the scattering properties are very different from 87 Rb. The Rb 2 molecular product distribution is mapped out in a state-to-state fashion using REMPI detection schemes which fully cover all possible molecular spin states. Interestingly, for the experimentally investigated range of binding energies from zero to ∼ 13 GHz × h we observe that the spin-conservation propensity rule also holds for 85 Rb. From these observations and a theoretical analysis we derive an understanding for the conservation of the hyperfine spin state. We identify several criteria to judge whether the propensity rule will also hold for other elements and collision channels.